I’ve lowered my front end 1.5cm, and was able to get my torso from 100 to 95 degrees at the seat height that I had all season, but now swapped out my cranks for 165mm (but thinking of going to 160mm now) from 170mm, then raised my saddle… my question is when looking at the max knee angle and trying to keep it in the range of 145 to 155. I noticed that when I put them in and before moving the saddle higher by 5mm, my knee angle with my foot at horizontal and BDC is like 160.
So, my confusion lies here: do you set the knee angle while pedaling and at (according to some fitters) at the normal cadence and under some intensity (on a trainer at say 80 to 85% FTP power) and see how your normal ankle foot knee angle action is? Or do you set it static with no motion?
I’m a flat pedaler at 90 degrees in the pedal stroke but most of the rest of the stroke through BDC I’m a toe dipper, maybe 1.5 to 2 cm from flat.
I saw Mat Steinmetz post that he now likes 135 to 145, is that in motion or at rest?
I have always been under the assumption its measured at motion. I dont see what benefit would be had measuring it static since it doesnt take into account how you pedal. For me for example, my ankle rotates as a pedal which makes my angle greater than held static so I measure it during motion since thats how I pedal. just my 2 cents.
I saw Mat Steinmetz post that he now likes 135 to 145, is that in motion or at rest?
I like 38-42 (142-138) degrees, but it really depends on the individual. I’d be perfectly happy with 35-44 degrees depending on the situation. These are taken in motion.
this is something one has to take care in assessing knee angle. As you raise a person’s saddle beyond their current area of comfort the weakest link in the system will change, most often that is the ankle. So yes when you shorten a crank you typically raise the seat to compensate on the change in leg extension. This will also open up the hip to upper leg angle, or open up the chest some. This may then allow you to accommodate the change in saddle to handle bar drop change. To get to the big question according to research by Dr. W. Peveler you need to perform knee angle measurements under motion and in general this is best at reasonable stress. So there are many things to consider when just looking at knee angles. Further, most people suggest a knee angle of between 25 and 35 deg of flexion 155- 145 of knee angle. Though I am not dedicated to these angles depending upon the rider and their flexibility etc. To look at only the knee angle is not a wholistic approach to fitting, there are a lot of other factors that need to be looked at to get a more full picture. One factor that comes into play with shortening the crank arm is that to achieve the same power at the same cadence you need to use a small amount more force on the pedals. It is not easily measured with a typical power meter because it is within their range of variability, 5mm change is around a 3% change in the force all other things being equal.
Since you have done a fair amount of fitting (an understatement, I know), I have a question that has come up based on my experience fitting a few riders: if one were to correctly set the optimum seat height in motion for a large group of riders, but then after the fact measure the knee angle for this same large group, would you find the static knee angle to be greater or smaller than that measured during motion? I ask this because I have seem some significant differences in these angles (static vs in motion) for most riders.
Then, kind of off topic, is there any decent supporting evidence for the a knee angle of 138 to 142 degrees as being optimal for cycling max power, submax power, efficiency, etc. If yes, got any links for any of these studies?
Thanks for the replies… I’m around 141 at the moment… I’ve had to lower the seat even with the shorter cranks. I had a FIST done about 2 years ago and he put my saddle at 91.5cm with 172.5mm arms back then, so about 1.5 years ago I put in 170’s but moved the seat to keep the 91.5, but when I put in the 165mm and put to 91.5, I was shocked to see that my angle was over 150 with that height. I use 91cm for my road bike with 170’s and gives me a nice angle of 140 and it’s comfortable… but at 91 on the TT, my leg is at nearly 150, so, I moved the saddle down to 90.5, I use that BIKE FIT app on the ipad… and at 90.5, the angle is about 140/141. But I was able to lower the front by 2 cm and still maintain hip space. The medium SHIV doesn’t allow a lot of drop in the stack when I had it in it’s lower positions already with the higher seat height… the lowest pad drop I could get was 9.25cm… torso was pretty high around 105 degrees… so, I got a 5mm top cap, negative 30 degree stem and I’ve got a drop of 11.25 now… now the torso is at 97. I’ve learned in this process that I have longish arms for my torso, so I sit up higher anyways.
I think that I saw on the web a study about seat height, just basicaly that the each individual should raise it as long as the power goes up and stop at the point where it begins to fall off… I don’t remember what the angle was though, but it seemed that the height was higher than most of those riders had been using.
Thanks for the replies… I’m around 141 at the moment… I’ve had to lower the seat even with the shorter cranks. I had a FIST done about 2 years ago and he put my saddle at 91.5cm with 172.5mm arms back then, so about 1.5 years ago I put in 170’s but moved the seat to keep the 91.5, but when I put in the 165mm and put to 91.5, I was shocked to see that my angle was over 150 with that height. I use 91cm for my road bike with 170’s and gives me a nice angle of 140 and it’s comfortable… but at 91 on the TT, my leg is at nearly 150, so, I moved the saddle down to 90.5, I use that BIKE FIT app on the ipad… and at 90.5, the angle is about 140/141. But I was able to lower the front by 2 cm and still maintain hip space. The medium SHIV doesn’t allow a lot of drop in the stack when I had it in it’s lower positions already with the higher seat height… the lowest pad drop I could get was 9.25cm… torso was pretty high around 105 degrees… so, I got a 5mm top cap, negative 30 degree stem and I’ve got a drop of 11.25 now… now the torso is at 97. I’ve learned in this process that I have longish arms for my torso, so I sit up higher anyways.
I think that I saw on the web a study about seat height, just basicaly that the each individual should raise it as long as the power goes up and stop at the point where it begins to fall off… I don’t remember what the angle was though, but it seemed that the height was higher than most of those riders had been using.
if it was only that easy. people to not actually respond that fast in my opinion. A new set up takes time to adjust to. It is like any other form of habit/ pattern, it takes a certain to change, so that does not work in my way of thinking. As you raise a seat there are other things to consider such as seat to bar drop and thus hip angle, eventually everyone will hit a point where they are not able to rotate their pelvis enough and also it will cause constriction of their breathing. Also (and I have seen this many times) our bodies react to space in a sense called proprioception, that is how it feels it is moving in space, I have seen as you raise he seat there is a point where the knee angle will not increase (or the flexion will not decrease). That is because most often they are opening the angle at the ankle, sometime they are dropping their hip… so if your fitter is not looking at the big picture then you may not achieve a good long term solution. As well they should be willing to work with you as you change either through better body function/ core strength or as you become accustomed to the new position and may be able to accommodate further changes. It is like stretching it takes time and is a progressive process.
if one were to correctly set the optimum seat height in motion for a large group of riders, but then after the fact measure the knee angle for this same large group, would you find the static knee angle to be greater or smaller than that measured during motion?
In my experience, you would see greater extension in the static measurements due to the ankle.
is there any decent supporting evidence for the a knee angle of 138 to 142 degrees as being optimal for cycling max power, submax power, efficiency, etc. If yes, got any links for any of these studies?
This is hard to say…most studies I’ve seen show greater extension than what most fitters recommend. But, from what I’ve seen in the field amongst age-group and professional triathletes and cyclist, 35-42 degrees is a good range to shoot for. My theory for the scientific research is that it was not done by a bike fitter and the points of measurement are most likely different. I know that FIST vs Retul points of location will give you a 2 degree “measurement” difference for the same knee angle.
Thanks Matt (just listening to an interview with you on a podcast!)
Have you seen anything regarding knee angles in those with cleats very aft/midfoot? I have moved my cleats right back, with cleat extenders from speedplay. Along with short cranks its really helped solve some of my hip issues. I have ended up with a fairly low saddle for my inseam and don’t seem to have any problem with it, but worry that I could be not getting close enough to full extension with the seat that low.
I also use Q-rings which may complicate things a bit!
Since I most ride my mountain and road bike during the off season, I’ve been dicking around with my fit on the SHIV for over a month by putting in everything from 172.5 to 165 and measuring… my first goal was to lower the stack as much as possible for the frame size and then if needed to use the pad spacers to raise the pads up. What I discovered was that whether I moved my saddle to a ridiculous height above any recommendations, or lowered below… I found that my leg seems to like 140 degrees approximately, meaning that I would flex my ankle what ever directions neccessary to achieve this… it kind of told me that that seems to be the limit of my flexibility. I’m 46… there was a time that I could have wrapped myself up into a ball from being flexible enough but that was 20 years ago… so I guess that I’ve found out accidentally where I am at, around Matt’s range of 138 to 142. I do remember however, that when I had a very high saddle, it put a huge strain on my back and in my right hamstring, not so much the mucle but the nerve bundle and tendons starting at the bottom of the lower back. I went to a sports rehab place and they did tests and propose that due to some lower back injuries in my early 20’s that I do have a slightly curved spine and more scar tissue on the right side, so I have to make my right side happy to be effective and the upper limit seems to be around that 140, even though my left side could theoretically extend out more. Whew! Sorry for the detail.
145 to 155 is too straight a leg. 145 is fine. but it’s on the high edge of fine. 143, 142 would be more like it, if you’re measuring to the center of the knee.
How does one determine the center of the knee, as seen from the side?
edit: Also related, how does one best determine the center of the ankle and hip, as seen from the side?
my landmarks: fulcrum center of knee, distal ends trochanter and maleolus. at bottom dead center (longest extension of the leg during the pedal stroke). note that these are landmarks, and not necessarily associated with the center of anything. for example, i’m not saying trochanter is the center of the hip. i’m just saying it’s a landmark. it doesn’t matter what you use as landmarks as long as your angular ranges conform to your landmarks.